The invention pertains to a transport device for rerouting flat mail pieces according to the preamble of claim 1.
Mail pieces are sorted in sorting stations in accordance with different criteria. These criteria, for example, can be addresses or bar codes. In such sorting machines, the flat mail pieces are transported clamped between cover bands that consist of a lower band and an upper band. In order to identify the respective sorting criteria, the mail pieces are transported in front of special cameras. The distribution information is recorded by these cameras and fed to evaluation electronics. Since a certain amount of time is required for this evaluation, the mail pieces can be sorted with the aid of guides only after this time has elapsed. This processing time is guaranteed by transporting the mail pieces, after the camera, along transport paths of greater or smaller length depending on the required evaluation time. Rerouting of the cover band paths is required along these transport paths in order to maintain a minimum space requirement.
According to DE 44 37 114 C1, the rerouting is realized with the aid of deflection rolls. The upper band is guided around a main drum. The lower band is guided past the main drum over an auxiliary drum, and the mail pieces are guided between the upper band and the main drum. If the spectrum of mail pieces necessitates large rerouting radii in order to prevent excessive bending stresses, drums with a large diameter need must be used. However, these large drums can only be manufactured with high costs and require twice the space for a 180E rerouting (only the semicircle is required).
According to DE 196 12 525, another variation for realizing rerouting consists of forming a curved path from individual rolls. The flat belts are rerouted by the curve of rolls. The disadvantage of this solution can be seen in the high cost for the large quantity of rolls required. A reduction in the number of rolls results in a polygon effect that highly stresses the mail pieces while they are transported through the curve and also leads to additional gap shifts. If the mail pieces contain carbon paper (e.g., forms, invoices), this can also result in the illegibility of the forms or invoices.
Consequently, the invention disclosed in claim 1 is based on the objective of developing an inexpensive transport device for rerouting flat mail pieces which has a small space requirement and which stresses the mail pieces as little as possible.
Through the guidance of the cover band system which consists of an endless lower band and an endless upper band over the stationary guide element with a sliding surface that is shaped in the form of a curved segment, the selection of different coefficients of friction presents a technical solution that requires a smaller depth for a large rerouting radius and consequently results in a reduced bending stress, with the manufacturing cost also being reduced.
Advantageous embodiments are defined in the subordinate claims.
At a given transport speed, the outer upper band must travel a longer distance than the lower band. In order to compensate for the resulting relative speeds without shifting or stressing the flat mail pieces, the inner side of the upper band is, according to claim 2, realized with a lower coefficient of friction.
According to claim 3, it is advantageous to realize the curved segment in the form of a segment of a circle.
In order to prevent uncontrolled runoff of the bands from the guide surface, the lower band is, according to claim 4, guided in the sliding surface of the guide element by means of a longitudinal groove.
It is also advantageous to realize the sliding surface of the guide element in an antistatic fashion according to claim 5.
According to claim 6, alignment sections are arranged at the ends of the guide element in order to compensate for inclined positions. The reception and the transfer of the mail pieces through the wider gap between the deflection rolls for the upper band and the lower band is simultaneously simplified.